The aim of this study is to elucidate the relationship between envelope elongation and events in the bacterial cell cycle such as DNA initiation, DNA replication, septum formation and cell division. Three stocks of Escherichia coli B/r having different patterns of DNA replication at equivalent growth rates will be used throughout the study. The proposed work will encompass 1) the characterization of the envelope phospholipids with respect to their composition and fatty acid moieties, 2) synthesis and turnover of the phospholipids during the cell division cycle, 3) phospholipid synthesis and turnover during amino acid starvation and during exposure to inhibitors of protein, RNA and DNA synthesis, 4) study of peptidoglycan synthesis during the division cycle. The study will be performed on synchronous growing populations of Escherichia coli. Macromolecular synthesis will be inhibited at various stages of the cycle and the envelope characteristics will be determined both during the inhibition and after resumption of synthesis as a function of the age of the cells at the time of inhibition. The study is expected to answer questions on the correlation between the DNA cycle and envelope synthesis, and should produce relevant information on the control of the duplication of a bacterial cell.